1. Field of the Invention
The present invention relates to a method for manufacturing the light-receiving device and a light-receiving device.
2. Description of the Related Art
Substances such as gases associated with environments or organisms such as animals and plants have the characteristics of absorbing specific infrared light including near-infrared light with a wavelength of about 2 μm to 10 μm. In order to detect the absorption spectra of the substances such as gases associated with environments or organisms such as animals and plants, infrared light-receiving devices are under development. In particular, in the near-infrared to infrared region, the photosensitivity to long-wavelength light is being improved. Here, the infrared light-receiving devices include a light-receiving layer containing a III-V group compound semiconductor. In the light-receiving devices, a planar-type photodiode structure forming a p-n junction by selective diffusion is used to reduce the dark current. In the planar-type photodiode structure, pixel separation is ensured by regions in which impurity (for example, Zn impurity) is not diffused.
Japanese Unexamined Patent Application Publication No. 2006-269978 (hereinafter referred to as Patent Document 1) discloses a mesa-type photodiode structure compared to the planar-type photodiode structure. In a light-receiving device disclosed in Patent Document 1, in order to ensure pixel separation, a groove of a mesa structure extends through a p-n junction in an indium gallium arsenide (InGaAs) light-receiving layer to a high-concentration impurity layer directly on an Indium phosphide (InP) substrate.
R. Rehm, et al., Type-II Superlatives; The Fraunhofer Perspective, Proceeding of SPIE, vol. 7660, 76601G-1 discloses a mid-infrared sensor including a light-receiving layer having an indium arsenide (InAs)/gallium antimonids (GaSb) type-II multi quantum well structure (MQS) on a GaSb substrate. This sensor includes a plurality of light-receiving portions (pixels). The pixels are separated by mesa structures. The mesa structures each have junctions (a pin junction and a nip junction) capable of receiving light with two wavelengths due to different quantum well thicknesses. Mesa grooves for element isolation are placed between the mesa structures. The mesa grooves extend through the pin or nip junctions. The mesa structures reliably separate the pixels included in this sensor.